Gas turbine burner hub with pilot burner

ABSTRACT

A burner arrangement for a combustion chamber for combustion of fluid fuels has a main burner and pilot burner arranged centrally within the main burner for the ignition and/or stabilization of the combustion of the main burner. The main burner has central fuel feed arrangement arranged around the pilot burner, an annular air duct surrounding the central fuel feed arrangement for the supply of combustion air, first fuel nozzles for injection of substantially gaseous fuel into the annular air duct. The first fuel nozzles are fed from a first fuel distributor in the central fuel feed arrangement, and second fuel nozzles for the injection of a substantially liquid fuel into the annular air duct are fed from a second fuel distributor in the central fuel feed arrangement. Ducts are provided which branch off from at least one of the fuel distributors and issue into the pilot burner.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2014/072741 filed Oct. 23, 2014, and claims the benefitthereof. The International Application claims the benefit of GermanApplication No. DE 102013222152.5 filed Oct. 31, 2013. All of theapplications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a burner arrangement, in particular a burnerarrangement with a main burner and a pilot burner, and to the mixing offuel with air.

BACKGROUND OF INVENTION

When operating a gas turbine plant, the mixing of fuel with air is ofcrucial significance, if optimum and consequently low-pollutantcombustion is to be achieved. For this purpose, fuel is injected in amaximally precisely metered manner and fed to the combustion air. Toachieve good mixing of the fluids, both the combustion air and the fuelare set in swirling motion by structural measures. This is typicallymainly achieved by curved vanes and fuel nozzles.

The increasingly stringent stipulations relating to pollutant reductionrequire constant improvement of combustion. Pollutants such as nitrogenoxides (NO_(x)) are mainly influenced by the mixing ratio of fuel to airand the efficiency of combustion. Complete combustion of the fuel isdesirable if pollutants are to be reduced.

Possible fuels are gaseous fuels, such as natural gas or synthesis gas,and also liquid fuels. It is precisely in the case of the liquid fueloil that nozzle geometry in combination with vane swirl has hithertoprimarily influenced mixing of said fuel with air. No further activeinfluencing of for example the depth of penetration of the fuel into theair stream or the swirling of the fuel and thus optimized mixing doesnot conventionally take place.

In the case of gas premixing injection, the gas is injected for examplevia bores in a swirl vane and premixed and swirled with the compressedair.

With both fuels, gas and oil, a pilot burner is typically used tostabilize the premixing flame. In the case of oil, this is an oildiffusion burner, while in the case of gas it is a pilot gas burner.

SUMMARY OF INVENTION

An object of the invention is to further develop the above-stated devicesuch that, when the device is in operation, maximally completecombustion is achieved.

According to aspects of the invention, this object is achieved by theburner arrangement according to the independent claim. Advantageousfurther developments of the invention are defined in the dependentclaims. In a burner arrangement for a combustion chamber, in particulara gas turbine combustion chamber, for burning fluid fuels, with a mainburner and a pilot burner arranged centrally therein, which pilot burnerserves to ignite and/or to stabilize main burner combustion, the mainburner comprising a central fuel feed arrangement arranged around thepilot burner, an annular air duct surrounding the central fuel feedarrangement for supplying combustion air, first fuel nozzles forinjecting a substantially gaseous fuel into the annular air duct,wherein the first fuel nozzles are supplied by a first fuel manifold inthe central fuel feed arrangement, and second fuel nozzles for injectinga substantially liquid fuel into the annular air duct, wherein thesecond fuel nozzles are supplied by a second fuel manifold in thecentral fuel feed arrangement, ducts are provided which branch off fromat least one of the fuel manifolds and lead into the pilot burner andthe pilot burner has a gas feed duct independent of the ducts, therebyensuring that the pilot flame is enhanced as a result of removal fromthe premixing passage of the diagonal swirler in the main burner andaddition to the pilot burner, whereby combustion is improved and theemissions therefrom are reduced.

In this case, it is convenient if the pilot burner comprises a pilotannular air duct for supplying combustion air and the ducts lead intothis pilot annular air duct.

To be able to supply the fuel as uniformly as possible to the pilotannular air duct, it is advantageous for the ducts leading into thepilot annular air duct to be uniformly distributed around thecircumference thereof.

In this respect it is convenient, because it is simple and inexpensiveto implement, for the ducts to take the form of bores.

In one advantageous embodiment, the ducts branch off from the secondfuel manifold and comprise nozzles at their ends leading into the pilotburner. The second fuel manifold for injecting a substantially liquidfuel, i.e. oil, is mechanically particularly stressed, such that it isparticularly advantageous here for the nozzles to be cavitation-free andscrew-fastenable should replacement be required.

With regard to the best possible intermixing of fuel and air, it isadvantageous for the annular air duct to comprise swirl vanes and forthe first fuel nozzles to be arranged in these swirl vanes.

The admixture of fuel from the central fuel feed arrangement does nothowever replace the independent supply of gas or oil in the pilotburner, but rather in combination therewith ensures additional fuelenrichment, for which reason in advantageous embodiments the pilotburner also comprises an oil feed duct independent of the ducts, inaddition to a gas feed duct independent of the ducts.

The additional mass flows according to the invention from the gas or oilmanifolds are mixed with the compressed air in the pilot gas line andthen combined with the fuel in the pilot burner. This makes possibleadditional fuel enrichment and mixing, which may lead to an improvementin the fuel/air mixture and thus to a reduction in pollutants.

The invention may also be implemented in an existing design by thesimple introduction of bores and/or nozzles.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE shows schematically, and not to scale, a burner arrangementaccording to the invention.

DETAILED DESCRIPTION OF INVENTION

The invention is described in greater detail below with reference to adrawing. The FIGURE shows schematically, and not to scale, a burnerarrangement 1 according to the invention, which may optionally be usedin conjunction with a plurality of similar burner arrangements forexample in the combustion chamber of a gas turbine plant. The burnerarrangement 1 has a main axis 19 and comprises a pilot burner 3 and amain burner 2 concentrically surrounding the pilot burner 3. Both pilotburner 3 and main burner 2 may optionally be operated with gaseousand/or liquid fuels, such as for example natural gas or heating oil. Thepilot burner 3 then comprises as fuel ducts an inner oil feed duct 18and an inner, annular gas feed duct 17 concentrically surrounding saidduct 18. This is in turn surrounded concentrically by a pilot annularair duct 13 for supplying combustion air 14.

In or on this pilot annular air duct 13 it is additionally possible toarrange a suitable ignition system (not shown in the FIGURE).

In the pilot annular air duct 13 there are additionally arranged swirlvanes 20, which comprise fuel nozzles 21 for supplying a fuel to astream 14 of oxygen-containing gas, typically air.

The main burner 2 surrounding the pilot burner 3 comprises, relative tothe main axis 19, a radially outer annular air duct 5 for the combustionair 6, through which extend a plurality of swirl vanes 16 of a swirlvane assembly. These swirl vanes 16 have as inlet for fuel first fuelnozzles 7, through which fuel gas may be injected into the air 6 flowingin through the annular air duct 5. The first fuel nozzles 7 are suppliedvia a first fuel manifold 8 in a central fuel feed arrangement 4. Asecond fuel manifold 10 in the central fuel feed arrangement 4 suppliessecond fuel nozzles 9 typically with oil.

The task of the pilot burner 3 is to maintain stable combustionoperation in the burner arrangement 1, since this is mostly operatedwith a lean mixture with a tendency towards instability.

In the example in the FIGURE, the invention provides not only ducts 11which branch off from the first fuel manifold 8 for the gas supply andlead into the pilot burner 3 but also ducts 12 which branch off from asecond fuel manifold 10 for oil. The ducts 12 have nozzles 15 at theirends leading into the pilot burner 3.

The ducts 11, 12 are distributed uniformly over the circumference of thepilot annular air duct 13 and may take the form of simple bores.

1. A burner arrangement for a combustion chamber for burning fluidfuels, comprising: a main burner and a pilot burner arranged centrallytherein, which pilot burner serves to ignite and/or to stabilize mainburner combustion, the main burner comprising a central fuel feedarrangement arranged around the pilot burner, an annular air ductsurrounding the central fuel feed arrangement for supplying combustionair, first fuel nozzles for injecting a substantially gaseous fuel intothe annular air duct, wherein the first fuel nozzles are supplied by afirst fuel manifold in the central fuel feed arrangement, and secondfuel nozzles for injecting a substantially liquid fuel into the annularair duct, wherein the second fuel nozzles are supplied by a second fuelmanifold in the central fuel feed arrangement, wherein ducts areprovided which branch off from at least one of fuel manifolds and leadinto the pilot burner and the pilot burner has a gas feed ductindependent of the ducts.
 2. The burner arrangement as claimed in claim1, wherein the pilot burner comprises a pilot annular air duct whichsupplies combustion air and the ducts lead into this pilot annular airduct.
 3. The burner arrangement as claimed in claim 2, wherein the ductsleading into the pilot annular air duct are uniformly distributed aroundthe circumference thereof.
 4. The burner arrangement as claimed in claim1, wherein the ducts take the form of bores.
 5. The burner arrangementas claimed in claim 1, wherein the ducts branch off from the second fuelmanifold and have nozzles at their ends leading into the pilot burner.6. The burner arrangement as claimed in claim 5, wherein the nozzles arecavitation-free and screw-fastenable.
 7. The burner arrangement asclaimed in claim 1, wherein the annular air duct comprises swirl vanesand the first fuel nozzles are arranged in these swirl vanes.
 8. Theburner arrangement as claimed in claim 1, wherein the pilot burnercomprises an oil feed duct independent of the ducts.
 9. The burnerarrangement as claimed in claim 1, wherein the combustion chambercomprises a gas turbine combustion chamber,